The major objective of this proposal is to investigate the molecular mechanisms of heavy metal-induced damage to nervous tissue. We are using monolayer cultures of rat glioma and mouse neuroblastoma (NB) cells as an experimental model. The studies will be performed after acute (4 days' treatment) and chronic (30 days' treatment) treatment of glioma and NB cells with methyl mercuric chloride (CH3HgCl). Glioma cells will be treated with CH3HgCl at 0.01, 0.05, and 0.1 microns, whereas NB cells will be treated at 0.01, 0.05, 0.1, and 0.5 microns. A concentration which does not produce any significant change on a given parameter after acute treatment will be selected for a chronic treatment in which cells will be incubated in the presence of this dose of CH3HgCl for a period of 10, 20, and 30 days before assaying for the biological parameter. The reversibility of an effect will be studied only after a dose-effect relationship is established for a chronic treatment. The following studies will be performed: (1) Changes in attachment efficiency, morphology, and growth rate. (2) Changes in the synthesis and phosphorylation activity in cytosol proteins, histone, and nonhistone chromosomal proteins. (3) Changes in total protein, RNA, and DNA synthesis. (4) Determination of biological half-life of radioactive CH3203HgCl in control and CH3HgCl-treated cells. (5) Changes in the sensitivity of adenylate cyclase to neurotransmitter (dopamine, norepinephrine, acetylcholine and PGE1). (6) Changes in the intracellular levels of cyclic AMP and cyclic GMP. (7) Changes in cyclic necleotide phosphodiesterase activity. (8) Changes in high affinity uptake of neurotransmitters (dopamine, norepinephrine, glutamate, glycine, choline, gamma-aminobutyric acid). (9) Effect of CH3HgCl in the presence of an elevated level of cyclic AMP for the criteria of morphological changes, growth rate, and biochemical functions.